Electrodiagnostic studies in ulnar neuropathy at the elbow
Summary statement of the American Association of Electrodiagnostic Medicine American Academy of Neurology and American Academy of Physical Medicine and Rehabilitation
Address correspondence and reprint requests to AAN, 1080 Montreal Ave., St. Paul, MN 55116.
Editor’s Note: The following is a summary statement ofthe American Association of Electrodiagnostic Medicine’s(AAEM) Practice Parameter for Electrodiagnostic Studies in UlnarNeuropathy at the Elbow. This summary statement of the practiceparameter was developed jointly by the Quality Assurance Committeeof the AAEM and the Quality Standards Subcommittee of the AmericanAcademy of Neurology and was endorsed by the AAN and AAPM&R.It is reproduced here with the permission of the AAEM.
Ulnar neuropathy at the elbow (UNE) is a common peripheral mononeuropathy,second only to carpal tunnel syndrome in incidence. The electrodiagnosticevaluation of UNE is frequently complex and challenging to eventhe most experienced electrodiagnostic medicine consultant.This document defines the standards, guidelines, and optionsfor electrodiagnostic studies of UNE based on a critical reviewof the literature.
A Medline search was conducted for literature in English from1983 through 1996 under the Medical Subject Headings (MeSH)1) ulnar nerve, 2) electrodiagnosis, 3) nerve compression syndromes,4) neural conduction, and 5) elbow. The initial search generated282 article titles with abstracts. The abstracts were reviewedby two AAEM Quality Assurance Committee members. Of the 282articles, 56 articles referring to electrodiagnosis and otherlaboratory studies to evaluate UNE were found and reviewed.The bibliographies of these 56 articles were examined and additionalarticles identified and reviewed. In total, 398 titles, abstracts,and papers were evaluated for inclusion in the review.
A total of 19 of the 398 articles and abstracts met five orsix literature classification criteria; six of these articleswere excluded from subsequent analysis for various reasons.For example, some investigators performed ulnar nerve conductionstudies (NCSs) in the course of looking primarily at other phenomena,such as the effects of age on the conduction properties of multiplenerves, the correlation between clinical and electrodiagnosticfindings, or the difference between proximal and distal nervesegments; the findings therefore have scant or no applicabilityto the evaluation of the clinical problem of UNE. Studies ofnormal control subjects met a maximum of five of five criteria;studies of patients with UNE met a maximum of six of six criteria.
The remaining 13 articles formed the basis for the recommendationsof this report. The findings of these and other additional studiesare reviewed in the Literature Review of the Usefulness of NerveConduction Studies and Electromyography in the Evaluation ofPatients with Ulnar Neuropathy at the Elbow, developed by theAAEM. This literature review is currently available throughthe AAEM Executive Office and will be published in a later issueof Muscle & Nerve. The conclusions and recommendations arebased on a review of Class A evidence from 702 normal controlelbows and 564 UNE elbows. The 13 articles reported sensitivitiesof electrodiagnostic studies ranging from 37% to 86% and specificitiesof 95% or greater.
Literature classification criteria.
1. Prospective study.
2. Diagnosis of UNE in the patient populationbased on clinicalcriteria independent of the electrodiagnosticprocedure underevaluation.
3. Electrodiagnostic proceduredescribed in sufficient detail,or reference provided to a publishedtechnique, to permit duplicationof the procedure; the positionof the elbow was stated and thesame elbow position used throughoutthe study.
4. Limb temperature monitored and reported.
5.Reference values for the electrodiagnostic procedure obtainedwith either a) concomitant studies of a reference populationor b) previous studies of a reference population in the samelaboratory.
6. Criteria for abnormal findings clearly stated,and definedin statistical terms, e.g., range, mean ±2 standarddeviations (SD), from data derived from the referencepopulation.
Definitions for classification of evidence.
1. Class A evidence: studies that meet all six literature classificationcriteria, or five criteria in the case of studies only on normalcontrol subjects.
2. Class B evidence: studies that meet fouror five literatureclassification criteria, or less than fivecriteria in the caseof studies only on normal control subjects.
3. Class C evidence: studies that meet three or fewer literatureclassification criteria.
The strength of a recommendation or conclusion is based on thequality and consistency of supporting evidence, as well as themagnitude of benefits, risks, and costs. The following ratingsystem is used:
1. Practice standards: generally accepted principles for patientmanagement which reflect a high degree of clinical certainty(Class A evidence).
2. Practice guidelines: recommendationsfor patient managementwhich reflect moderate clinical certainty(Class B evidence).
3. Practice options/advisories: otherstrategies for patientmanagement for which the clinical utilityis uncertain (ClassC evidence).
The following conclusions and recommendations are made for theelectrodiagnostic medicine evaluation of patients with suspectedUNE. The recommendations are given in greater detail in theliterature review developed by the AAEM. These recommendationsare practice guidelines unless otherwise indicated.
General principles:
1. Ulnar sensory and motor NCSs should be performed with surfacestimulation and recording. Limb temperatures should be monitoredand maintained in a reference range and should be reported ifoutside a reference range. Corrections in conduction for temperature,if any, should be indicated in the report, although warmingcool limbs and repeating the studies is preferable when possible.This recommendation is a practice standard.
2. If ulnar sensoryor motor NCSs are abnormal, further NCSsshould be carried outto exclude a diffuse process. This recommendationis a practicestandard.
Elbow position:
3. Ulnar motor NCS reports should specify the elbow positionused during the performance of the studies and the referencevalues employed. The technique used should be the same as thatused to determine the reference values. The same elbow positionshould be employed during both stimulation and measurement.This recommendation is a practice standard.
4. The most logicalelbow position for ulnar NCSs is moderateflexion; 70° to90° from horizontal. Moderate flexionprovides the greatestcorrelation between surface skin measurementand true nervelength.
5. Across-elbow distances used in evaluations performedwiththe elbow in moderate flexion have been in the range of10 cm;this distance correlates best with published referencevalues.However, studies performed over this distance may maska focalabnormality. Normal results over a 10-cm distance mayoccurdespite a significant focal lesion.
6. Stimulation morethan 3 cm distal to the medial epicondyleshould be avoidedas the nerve is usually deep within the flexorcarpi ulnarismuscle by this point and there is substantialrisk of submaximalstimulation.
Technique:
7. When using moderate-elbow flexion, a 10-cm across-elbow distance,and surface stimulation and recording, the following suggesta focal lesion involving the ulnar nerve at the elbow: Multipleinternally consistent abnormalities are more convincing thanisolated abnormalities, which raise the possibility of artifactor technical mishap. (Note: The following are listed in orderof strength of evidence):
a. Absolute motornerve conduction velocity(NCV) from above elbow (AE) to belowelbow (BE) of less than50 m/s.
b. An AE-to-BE segment greaterthan 10 m/s slower than the BE-to-wrist(W) segment. The literatureis inadequate to make a recommendationregarding the percentof slowing.
c. A decrease in compound muscle action potential(CMAP) negativepeak amplitude from BE to AE greater than 20%;this suggestsconduction block or temporal dispersion indicativeof focaldemyelination. This presumes that anomalies of innervation,i.e., Martin-Gruber anastomosis, are not present.
d. A significantchange in CMAP configuration at the AE sitecompared to theBE site. This presumes that anomalies of innervation,i.e.,Martin-Gruber anastomosis, are not present.
e. Nerve actionpotential (NAP) recording may aid in diagnosis,especially inpatients with only sensory symptoms. However,NAP studies havesignificant pitfalls and limitations. Beforerelying on changesin NAP amplitude or conduction velocity (CV)as a diagnosticcriterion for UNE, the examiner should be fullyaware of thecontent and technical details of the applicableliterature.Abnormalities of the distal sensory or mixed NAP,especiallyloss of amplitude, are nonspecific and nonlocalizingfeaturesof UNE.
f. The literature is not adequateto makea recommendation regarding conduction through the AE-to-WorBE-to-W segments.
8. If ulnar motor conduction studieswith stimulation at thewrist, above and below the elbow recordingfrom the abductordigiti quinti are inconclusive, the followingprocedures maybe of benefit:
a. NCSs recordedfrom the first dorsal interosseous(FDI) muscle. Because ofdifferential fascicular involvement,fibers to the FDI may showabnormalities not evident when recordingfrom the abductor digitiminimi.
b. An inching study, exploring for changes in theCMAP amplitude,area or configuration, or for abnormal changesin latency overprecisely measured 1- or 2-cm increments fromAE to BE. Themost convincing abnormality involves both a changein latencyand a change in either amplitude, area, or configuration;however,latency changes in isolation may be significant.
c.With severe UNE, distal wallerian degeneration may slow theBE-to-W segment secondarily and make localization difficult.Comparison of the AE to BE segment with the axilla-to-AE segmentmay be useful under such circumstances, but normative data isscant. This recommendation is a practice option.
d. NCSs toforearm flexor muscles are not generally useful,but may beemployed as a last resort with awareness of the technicallimitationsand the applicable literature. This recommendationis a practiceoption.
e. Depending on the results of NCSs, needle electromyography(EMG) may be indicated. Needle examination should always includethe FDI muscle, which is the most frequent muscle to demonstrateabnormalities in UNE, and ulnar innervated forearm flexor muscles.Neither changes limited to the FDI, nor sparing of the forearmmuscles, exclude an elbow lesion. If ulnar innervated musclesare abnormal, the examination should be extended to includenonulnar C8/medial cord/lower trunk muscles, to exclude brachialplexopathy, and the cervical paraspinals, to exclude radiculopathy.
1. Future evaluations of electrodiagnostic studies in UNE patientsbe constructed to:
a. Meet all six literatureclassificationcriteria described in this report.
b. Reportthe specific clinical criteria used for the diagnosisof UNE.
c. Include calculation of the sensitivity and specificityofthe test results.
d. Include sufficient data to permitcomparison to the resultsof previously published studies.
2.An outcome study be performed to assess the harm, benefit,andcost of performing NCSs and needle EMG in patients withsymptomssuggestive of UNE. The value of electrodiagnostic studiesinpredicting treatment outcomes, including surgery, deservefuturestudy.
3. The AAEM reviews this report every 5 years and updatesthereport as necessary.
Acknowledgments
Disclaimer. This report is provided as an educational serviceof the AAEM. It is based on an assessment of the current scientificand clinical information. It is not intended to include allpossible methods of care of a particular clinical problem, orall legitimate criteria for choosing to use a specific procedure.Neither is it intended to exclude any reasonable alternativemethodologies. The AAEM recognizes that specific patient caredecisions are the prerogative of the patient and his or herphysician and are based on all of the circumstances involved.
For review and critique of the manuscript, we acknowledge theassistance of Michael T. Andary, MD, MS; Francis J. Bonner Jr.,MD; Neil A. Busis, MD; Andrew A. Eisen, MD; Sudhansu Chokroverty,MD; Janice L. Cockrell, MD; Les Dorfman, MD; Donna L. Frankel,MD; Earl R. Hackett, MD; Gerald J. Herbison, MD; M. David Jackson,MD; Kevin R. Nelson, MD; Mark Hallett, MD; Charles K. Jablecki,MD; James A. Leonard Jr., MD; Robert G. Miller, MD; Trilok N.Monga, MD; Richard K. Olney, MD; Gareth J.G. Parry, MBChB; AtulT. Patel, MD; Donald B. Sanders, MD; Yuen T. So, MD, PhD; J.Clarke Stevens, MD; John D. Stewart, MBBS, FRCP(C), MRCP; RobertL. Sufit, MD; Cheryl F. Weber, MD; Jacqueline J. Wertsch, MD;John R. Wilson, MD; Shirlyn A. Adkins, JD; Lori H. Hattenhauer,JD, MBA; and, especially, John C. Kincaid, MD.
For review and critique of the manuscript, the AAN acknowledgesthe assistance of the members of the Quality Standards Subcommittee:Milton Alter, MD, PhD; Stephen Ashwal, MD; John Calverley, MD;Richard M. Dubinsky, MD; Gary Franklin, MD, MPH; JacquelineFrench, MD; Michael K. Greenberg, MD; Gary Gronseth, MD; DeborahHirtz, MD; Robert G. Miller, MD; Jay Rosenberg, MD; James Stevens,MD; and Catherine A. Zahn, MD.
For review and critique of the manuscript, the AAPM&R acknowledgesthe assistance of Dennis J. Bonner, MD; Mary L. Dombovy, MD;Lisa S. Krivickas, MD; Michael Y. Lee, MD; Ib R. Odderson, MD,PhD; Randolph B. Russo, MD; and Faren H. Williams, MD.
Footnotes
Developed by the AAEM Quality Assurance Committee: William W.Campbell, MD, MSHA, Chair; Dorothy J. Carroll, MD; Michael K.Greenberg, MD; David A. Krendel, MD; Rhonda M. Pridgeon, MD;Kadambi P. Sitaram, MBBS; and Faren H. Williams, MD.
Summary Statement approved by the AAEM Board of Directors: 1997.
Received September 21, 1998.
Accepted in final form September 22, 1998.
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Introduction
Introduction.
